1. Field of the Invention
The present invention relates to a bolt automatic tightening and untightening method and apparatus therefor for automatically tightening and untightening a bolt/nut (a thread member) serving as an assembling and fastening device for a divisible form used in centrifugal compacting and molding of concrete products such as poles, piles, etc.
2. Description of the Prior Art
For example, as shown in FIGS. 24 (a), 24 (b) and 24 (c), the aforementioned form 1 comprises two lengthy split forms la and la having a semicircular section, and each split form la has a reinforcing rib 1c axially projected substantially at a central portion of an outer peripheral surface thereof. Both the split forms 1a and 1a are formed into a cylindrical shape having a substantially round section by jointing respective flanges 1b projected from opposite ends of the split forms la and la to each other.
Disassembling or assembling of the form 1 is carried out by tightening and untightening plural sets of bolts 3 and nuts 4 provided at positions of flanges 1b spaced by a predetermined distance in an axial direction of the form 1 from a plurality of annular tires 2 (rotary supports) projected from the outer peripheral surface of the form 1 along the axis of the form 1.
The tires 2 are provided to rotatably support the form 1 when the form 1 filled with concrete is rotated to perform centrifugal compacting and molding of concrete products.
The apparatus for automatically tightening and untightening the bolt 3 is known, for example, from Japanese Patent Laid-Open No. hei 1- 216806.
FIGS. 25 and 26 show a bolt automatic tightening and untightening apparatus disclosed in the aforementioned Japanese Patent. FIG. 25 is a front view, and FIG. 26 is a side view.
As shown in FIGS. 25 and 26, split forms 101a and 101b substantially similar to the split forms 1a and 1a of the aforementioned form 1 comprise lengthy semicircular cylindrical bodies 101d and 101e, flanges 101c provided on semicircular opposite ends of the bodies 101d and 101e, and semicircular annular tires 102 axially projected from the outer peripheries of the bodies 101d and 101e. A form 101 comprises two flanges 101c jointed opposedly to each other, and a plurality of the tires 102 as strengthening members provided on the form 101 in an equal interval. Disassembling or assembling of the form 101 is carried out by tightening and untightening a number of bolts 103a and 103b provided on the flanges 101c. In FIG. 26, the phantom line X designates the center axis of the form 101.
In the bolt automatic tightening and untightening apparatus 104, a U-shaped frame 105 is provided so as to stride over a moving space of the form 101. The form 101 is placed on the upper surface of a carriage 106, which is in turn movable in a direction as indicated by arrows 119 and 120 on a set of rails 107.
A body 108 of a bolt tightening and untightening mechanism for automatically tightening and untightening bolts 103a and 103b of the form 101 is supported on the frame 105 in such a way as to be freely moved in the direction as indicated at the arrows 119 and 120 by means of a slide bearing 109, the body 108 being moved relative to the frame 105 by means of an air cylinder 110 provided on the frame 105.
In this bolt tightening and untightening mechanism, a plurality of tightening and untightening devices 111 composed of impact wrenches or the like are arranged on the body 108 in such a way that every two devices 111 are opposed to each other in order to tighten and untighten the bolts 103a on the flanges 101c projected from the split forms 101a and 101b. The two opposed tightening and untightening devices 111 can be moved in the form of one set in a direction as indicated at arrows 121 and 122 as well as up and down (in a direction of thread of bolt 103a). A socket 112 at the extreme end of the tightening and untightening device 111 can be replaced. On the body 108 of the bolt tightening and untightening mechanism, a clamper plate 116 is hung toward the form 101, so that the clamper plate 116 is engaged with the tire 102 provided on the outer peripheral surface of the form 101 whereby the body 108 of the bolt tightening and untightening mechanism can be moved on the rails 107 of the frame 105 as the form 101 moves.
The clamper plate 116 is mounted to be moved up and down by means of an air cylinder 117, and can be engaged with or disengaged from the tire 102.
The operation of the bolt automatic tightening and untightening apparatus will be described hereinafter.
When the form 101 is moved in the direction of the arrow 119 and the passage of the tire 102 of the form 101 is detected by a limit switch 118, the clamper plate 116 is moved down. When the form 101 is further moved in the direction of the arrow 119 and the tire 102 comes into engagement with the clamper plate 116, the form 101 in close contact with the body 108 moves in the direction of the arrow 119. The tightening and untightening device 111 is moved down during movement of the body 108 in the direction of the arrow 119, and the bolt 103a is tightened and untightened by the socket 112 of the tightening and untightening device 111.
Upon termination of the tightening and untightening operation of the bolt 103a, the tightening and untightening device 111 and the clamper plate 116 are moved upward to avoid contact with the tire 102, and the body 108 is moved in the direction of the arrow 120. Then, it engages a next rotary support to stand-by for operation of tightening and untightening the bolt 103b.
Naturally, the tires provided on the form are different in size, as well as the form, according to the kind of concrete products.
However, the conventional automatic tightening and untightening apparatus has a problem in that since a moving amount of the clamper plate engaged with the tire is preselected and constant, the moving amount of the clamper plate needs to be adjusted when the kind of the form is changed and its operation is extremely cumbersome for an operator.